SILESIA. 165 SILITJS ITALICXTS. first and second Silesian wars. At the close of the Seven Years' War (q.v.), in 1763, tlie bulk ol .Silesia wan ilctinitively ceded to Prussia. Bii;i.U)(;R.riiY. SchroUer, /Sc/i/csien (Glogau, 188.5-88) ; Kosiiiann, Oberschlesicn, sein Land ■and seine Industrie (Gleiwitz, 1888) ; Adamy, tichlcsie)i nach scinen physihalischen, toi)<j(iriipk- ischen und statistischen ^'erhiillnissen (Ttli ed., Breslau. 1803) ; Partscli, Sclilesien, eine Land- cskiindc auf wissenschaftlichey Orundlagc (Bres- lau, 1896) : Gruenhagen, Geschichte Sehlesiem (Gotha, 1884-86). SILESIA, Austrian. A duchy and crownland of the Au>trian Empire, bounded by Prussian Silesia on the north and west, Galieia on the east, and Moravia on the south (ilap: Austria, El). Its area is 1987 square miles. The Su- detie chain enters Silesia from the west, and the Carpathians send off several spurs into the in- terior from the east, giving the surface an ex- tremely mountainous character. The chief rivers are the Oder and the Vistula, both rising in the province. The climate is raw, but, on the whole, healthful. Agriculture is carried on in the val- leys, where good crops of cereals and industrial plants are raised. The mountain regions are chiefly utilized for cattle-raising. Silesia is one of the chief coalmining districts of Austria, with an annual output of from 4.000.000 to 5.000,000 tons. Favored by its abundance of fuel, Silesia has a number of well-developed manufacturing industries. Ironware, textiles, beer, and spirits are the chief products. Silesia has a Diet of 31 members, and is represented in the Lower House of the Austrian Reichsrat by 12 members. Pop- ulation, in 1900, 680,,529. of whom over four- fifths were Roman Catholic. According to na- ticmality the population of 1890 was divided as follows: 44 per cent. German, 22 per cent. Czech and Slovak, and over 30 per cent. Polish. Cap- ital. Troppau (q.v.). For history, see Silesia. SILEX (Lat., flint). A generic niime formerly used by mineralogists to designate those min- erals of which silica is the principal ingredient. SILICA, or Silicic Acid. See Silicon; Quartz. SILICIDE OF CARBON, or Carbide of Silicon. See Carkides. SILICEOUS HOCKS. A group of sedimen- tary rocks characterized by quartz as the prin- cipal constituent. Sandstone, quartz conglom- erate, arkose, novaculite, and chert are the chief varieties of siliceous rocks. SILICON (Nco-Lat., from Lat. silex, flint), or Silicium. a non-metallic element discovered by Berzelius in 1823. Among the ancients minerals ■ rich in silica were used in glass-making, and Becher contended that they contained a pecu- liar kind of earth, to which he gave the name terra ritrescihilis. In the seventeenth century it was found that such minerals did not change when heated by themselves, and only formed a fusible glass when brought in contact with other bodies. In 1660 Taehenius showed that it pos- sessed acid rather than alkaline properties, as it combined with alkalies, but the true nature of silica remained unknown until Davy demon- strated it in the early part of the nineteenth century. Silicon is the most abundant of all elements in the solid earth's crust, with the ex- ception of oxygen. It is never found in the iso- lated state, but occurs in combination with oxy- gen as silicon dioxide or silica (quartz. Hint, sand, etc.), and in various minerals in the form of metallic silicates. It is also found in mineral springs and in sea water. It was originall}' pre- pared by Berzelius by decomposing ))otassiura silicolluoride by means of potassium in an iron tube at a red heat. When allowed to cool, the mass was treated w'ith water, which dissolved the potassium lluoride. leaving silicon in the form of an amorphous brown powder. This method is still used, l)ut with the substitution of sodium for potassium. The element may also be obtained by the electrolysis of a fised mix- ture of potassium fluoride and silicofluoride. A graphitoidal modification of silicon is recognized by some, and may be produced by heating amorphous silicon in a platintmi crucible; while a third modification, known as crystalline or adamantine silicon, is formed by heating in an earthenware crucible a mixture of three parts of potassium fluosilieate. one part of sodium in small pieces, and four parts of granulated zinc. Silicon (symbol Si; atomic weight, 28.40), when in an amorphous condition, is a lustrous brown powder, which does not conduct electric- ity and is fusible in a non-oxidizing atmosphere at a temperature between the melting-points of steel and cast iron. The graphitoidal modifica- tion consists of shining metallic scales: while crystalline silicon is obtained in the form of grayish-black metal-like leaflets or needles, with a specific gravity of 2.19, and a melting-point between 1100" a"nd 1300° C. Silicon combines directly with a number of the elements, forming silicidcs. With oxygen silicon combines to form only one oxide, the dioxide, or silica (Si02), which is an important constituent of the solid crust of the earth and may be artificially pre- pared by burning silicon in air or oxygen. As flint and as sand it has many .applications in the arts, as in the manufacture of glass, pottery, etc. Silicon unites with the halogens. Thus, with fluorine, it forms a silicon tetrafluoride, which is a colorless gas that combines with water, forming hydrofluosilicic acid, which in turn unites with bases to form salts known as silico- flnoridcs. SILIPAN,. se'Ie-pan'. A Malay tribe in Xueva Vizcava Province, Luzon; speech, Ifugao. See Philippine Islands. SILISTBIA, si-lls'trl-a. A town of Bul- garia, on the right bank of the Danube, 75 miles below Rustchuk (Map: Balkan Peninsula, F 2). In the vicinity are vineyards and tobacco planta- tions, and the town produces flour and leather on a considerable scale. Population, in 1900, 12,133. Silistria was called by the Romans Durostoriim and was an important city of Moesia Inferior. It was an important fortress under the Turkish rule and repeatedly baffled the at- tacks of the Russians. SII/IUS ITAL'ICTJS, Tiberius Catius (25- 101). A Latin poet, wliose name appears fre- quently in Martial and Pliny. He was probably a delator under Nero. In 69 he was consul, and soon after proconsul in Asia. He was rich and luxurious, a dilettante in literature, art, and philosophy, being a member of the Roman school of Stoics and a friend of Epictetus. He starved himself rather than linger with an incurable dis- ease. A Homerus Laliniis, or Pindarus Thebanus,
